Haptic Systems 530 655 Mohsen Mahvash Lecture 2

Haptic Systems 530 -655 Mohsen Mahvash Lecture 2 9/1/06 1

Generating Force-Feedback with a Manipulator Ø Tip of a kinesthetic Haptic display and degrees of freedom Ø Relation between the tip position and joint angles Ø Encoders and measuring joint angles Ø Relation between joint torques and forces at the tip Ø Jacobean Ø Actuator equations Ø Nonidealities of a haptic device Ø Discussion Ø References 2

Tip of a Kinesthetic haptic display v v v A point of haptic display whose position and orientation are used for haptic simulation Through this point human user interacts with haptic systems Haptic simulator defines the force and torques should be generated at this point by the manipulator Degrees of freedom of a haptic display: The number of directions that a haptic display can pivot or move its tip DOF of motion DOF of sensing DOF of actuation 3

Tip Location and Degrees of Freedom Sens. Able Phantom Omni DOF of motion: 6 DOF of sensing: 6 DOF of actuation: 3 Tip 4

Tip Location and Degrees of Freedom MPB 6 S DOF of motion: 7 DOF of sensing: 7 DOF of actuation: 6 Tip 5

Tip Location and Degrees of Freedom da Vinci Master (From US Patent 06714839) DOF of motion: 7 DOF of sensing: 7 DOF of actuation: 7 Tip 6

Tip Location and Degrees of Freedom Haptic scissors DOF of motion: 2 DOF of sensing: 2 DOF of actuation: 2 Tip? 7

Relation Between Tip Position and Joint Angles (Forward Kinematics) 8

Encoders Small discs that have holes in them that can be read by photo sensors. The photo sensors record the number of transitions between light and dark. Disc Photo detector Light beam generator Initializations: Potentiometers and fixed setting points 9

Relation between Joint Torques and Forces at the tip n Principal of virtual work n Jacobian 10

Jacobian Taking partial derivatives 11

Actuators Equations n Torque n Voltage n Input Current amplifier: I as an input Voltage amplifier: V as an input 12

Nonidealities of a haptic device Ideal haptic devices Ø No friction Ø No Inertia Ø High bandwidth Actual haptic devices 13

Discussion Ø Ø Ø Ø High fidelity haptic devices Friction Inertia gravity Device bandwidth Sensors Actuators 14

References Introduction to Robotics Mechanics and Control, 2 nd Ed. , John J. Craig, Addison- Wesley (Chapter 3 and 5. 7 to 5. 11) Tomorrow Introduction to haptic rendering 15